As shown in FIG. 1, a conventional underwater pipe assembly used for pumping seawater includes two adjacent pipes 1 and a connector apparatus. Each pipe 1 has a pipe body 101 extending along a longitudinal axis, and two annular flanges 102 projecting radially, outwardly and respectively from two opposite ends of the pipe body 101. The flange 102 at one end of one of the pipes 1 abuts against the flange 102 at a corresponding end of the adjacent pipe 1. The connector apparatus includes a plurality of angularly spaced-apart connecting units 2 disposed around the abutted flanges 102 of the adjacent pipes 1. Each of the connecting units 2 includes two clamp plates 201 respectively abutting against the flanges 102 of the adjacent pipes 1 that abut against each other, and a fastener 202 securing the clamp plates 201 so as to clamp the abutted flanges 102 of the adjacent pipes 1 therebetween. By using the connector apparatus 2, the use length of the pipes 1 may be extended.
However, when a fastening force of the fastener 202 to secure the two clamp plates 201, each having an I-cross section relative to the longitudinal axis, is excessive, the clamp plates 201 are likely to deviate such that inner portions thereof move away from each other and outer portions thereof move toward each other. This causes the connecting effect of the connector apparatus to be poor which in turn may cause leakage of seawater during pumping.